(19)
(11) EP 0 534 432 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
23.02.1994 Bulletin 1994/08

(43) Date of publication A2:
31.03.1993 Bulletin 1993/13

(21) Application number: 92116367.1

(22) Date of filing: 24.09.1992
(51) International Patent Classification (IPC)5: C21D 8/12, C21D 11/00, C21D 3/04
(84) Designated Contracting States:
DE FR GB IT

(30) Priority: 26.09.1991 JP 248091/91

(71) Applicant: NIPPON STEEL CORPORATION
Tokyo 100 (JP)

(72) Inventors:
  • Minakuchi, Masayoshi, c/o Nippon Steel Corp.
    Kitayushu-shi, Fukuoka (JP)
  • Kondo, Yasumitsu, c/o Nippon Steel Corp.
    Kitayushu-shi, Fukuoka (JP)
  • Ishibashi, Maremizu, c/o Nippon Steel Corp.
    Kitayushu-shi, Fukuoka (JP)

(74) Representative: VOSSIUS & PARTNER 
Postfach 86 07 67
81634 München
81634 München (DE)


(56) References cited: : 
   
       


    (54) Process for production of oriented electrical steel sheet having excellent magnetic properties


    (57) A slab for an electrical steel sheet is heated at a temperature of 1280°C or below and then hot-rolled. The hot-rolled steel sheet or hot rolled and annealed steel sheet is then cold-rolled once or at least twice with intermediate annealing being performed between rollings. The cold-rolled sheet is decarburized and nitrided to form an inhibitor. The amount of nitrogen of in the steel sheet during the nitriding treatment subsequent to the decarburization annealing and the iron loss value after the withdrawal of the steel sheet from the furnace are measured to estimate the average diameter of a primary recrystallized grain, and next decarburization annealing is performed under conditions regulated in such a manner that the average diameter of the primary recrystallized grain of a product sheet falls within a proper range. The steel sheet subjected to the decarburization annealing is coated with an annealing separator composed mainly of MgO and then subjected to finish annealing.






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